Identification of Methane Emissions in an Urban Setting ESRL - - PowerPoint PPT Presentation

Identification of Methane Emissions in an Urban Setting

ESRL Global Monitoring Annual Meeting May17-18, 2011

• Nathan Phillips & Lucy Hutyra – Boston University
• Jocelyn Turnbull & Colm Sweeney – NOAA/ESRL
• Paul Shepson & Maria Obiminda Cambaliza – Purdue
• Eric Crosson, Chris Rella, & Sze Tan – Picarro, Inc.
• Robert Ackley – Gas Safety, Inc.

Collaborators in this effort

• As an extension of the INFLUX work

– Identify methane source locations and gather information

• n methane flux signals (relative magnitudes).
• Provide prior knowledge for inversion models.
• Data to help validate inversion model results.
• Information to help improve flux measurements from aircraft.
• Data could help to model cross-wind dispersion in an urban

environment.

Objectives of this effort

Method: Measuring Methane Plumes to Determine Source Locations

Methane Source

Wind

methane plume

• Map out methane concentrations

while driving along roads and highways.

– CH4: 2 ppb precision at 0.5 Hz. – GPS data – Wind velocity

Method: Identifying methane source locations

Sources Reconstruction Guidance from Simple Gaussian Plume Model

Source locations calculate from plumes

methane source and plume roads

Four source locations Winds: 0 to 360

• in 20
• steps

Atmospheric stability class C

Model Results: Winds from only two orthogonal directions…….source location looks possible.

Class A

Sources Reconstruction

Atmospheric Stability Class F

From Models to Reality: Measurements in Indianapolis

108.560 108.561 108.562 108.563 108.564 5 10 15 20 25 30 35 40

Methane (ppm) PlumeRUN1-4_19_2011-Data-landfill

Methane Concentration (parts per million)

Methane Measurements Taken While Driving

Distance Traveled

Methane measurements while driving through plume

“Methane Maps” of Indianapolis

Wind direction, 23km/hr

1 2 3 4 5

Some Sources are easy to Identify

1 2 3 4 5

> 25 ppm

Others are NOT so Easy

1 2 3 4 5

Methane Data Taken the Next Day

Wind direction, 23km/hr

1 2 3 4 5 6 7 8

Reproducibility of Plume Measurements

45 minutes

Repeated landfill plume measurements taken while driving 2 km from source. (Location: Danville, IN)

• Wind speed = 3.8 ± 1.2 km/hr
• Source Flux ≅ 7,000 grams / minute

1.5 km

High variability in plume shape. Take advantage by……

Stationary Tracer Method to Assess Fluxes

• Fixed location 1300 m downwind of landfill
• Natural variation in wind direction & wind speed will cause variability in

signal as the plumes sweep across the detection point

• High correlation indicates good overlap between plumes

methane acetylene

Landfill

Wind

methane plume tracer plume

Methane Flux Determination (Location: Danville, IN)

• Plot methane vs.

acetylene.

• Slope of line

gives ratio of emission rates.

= 7.5 moles / s

A Very Complex Methane Map: Boston

Play Video

Natural Gas Leaks in and around Boston

Natural Gas Leaks Destroying Vegetation

• Leaks in aging natural gas pipelines are killing trees all

across the northeast.

– Natural gas leaks can kill trees by displacing oxygen in the soil and drying out their roots. – 7,500 to 10,000 trees affected in Boston area alone.

• Several cities are asking for damages in excess of $1M

each.

http://natgaspollutes.com Flux (cubic feet / m2-day) at surface Gas in air 8” below surface

0.237 26% 1.407 48% 1.007 80% 0.012 63%

• Identification of methane source locations by

driving around looks possible.

• Flasks need to be analyzed.
• Need model to reconstruct methane probability

distribution from plume data.

• Need to take more systematic data.

Summary